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Date: Fri, 25 Sep 2015 16:13:44 +0100
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To: =?UTF-8?Q?Johannes_Schl=C3=BCter?= <johannes@schlueters.de>
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Subject: Re: [PHP-DEV] Implementing Generics, and none scalar default properties.
From: codekestrel@googlemail.com (Dominic Grostate)

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Hi,

I see what you mean with static properties, that would be more difficult.
I can answer on non-static however.

* When will $p2 be initialized, which properties can it access?

- On class instantiation.  It won't have access to $this, because the
object won't have been created yet.  It will have access to the same
entities as a static method.

* In B's constructor we're overwriting $p1, so $p2 will be initialized with
the wrong value.

- It won't have access to $this.  In effect they are pre-constructor
assignments, just like any other property.

Concerning reassignment on constructor leading to wasted code, I can only
place faith in the effectiveness of the user to override those properties
to NULL.

Anyway sorry about the mixed post.  I've mainly been working on
implementing generics, so I have a separate thread somewhere for that.

Dominic
On 25 Sep 2015 1:09 pm, "Johannes Schl=C3=BCter" <johannes@schlueters.de> w=
rote:

> Hi,
>
> Would be good to split complete different subjects to different threads
> anyways:
>
> On Wed, 2015-09-23 at 15:53 +0100, Dominic Grostate wrote:
> > the
> > ability to set default values of properties to instances of objects or
> > calls to static methods or functions (expressions in general).
>
> This causes questions on the order of execution and leads to waste of
> CPU time in case the constructor overrides the default value while not
> bringing much benefit over initialization in the constructor. It also is
> complicated regarding exceptions being thrown.
>
> Take the following code:
>
> <?php
>
> foo();
>
> class A {
>    protected $p1 =3D new Something();
>    private $p2 =3D new SomethingElse($this->p1, $this->p3);
>    private $p3 =3D new Something();
>    private static $s1 =3D new StaticSomething();
>
>    public function __construct() {}
> }
>
> bar();
>
> class B extends A {
>     private $p4 =3D new Something();
>
>      public function __construct() {
>          parent::__construct();
>          $this->p1 =3D new Whatever();
>      }
> }
>
> baz();
>
> try {
>     $b =3D new B();
> } catch (Exception $e) {
> }
> ?>
>
> Some Questions:
>
>       * Where, relative to foo(), bar() and baz() will StaticSomething's
>         constructor be called? How do you capture exceptions from there?
>       * When will $p2 be initialized, which properties can it access?
>         (Only the ones initialized before? None?)
>       * In B's constructor we're overwriting $p1, so $p2 will be
>         initialized with the wrong value.
>
> I'm sure there are more questions ... doing this i the constructor makes
> things clear and explicit with about the same amount of code to write.
>
> johannes
>
>

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